With some 2,000 interviews captured in 80 shoots in 50 countries around the world, all shot in 4K or bigger, filming for Yann Arthus-Bertrand's Woman project generated a vast amount of footage. Agent editor Philippine Merolle and director of post-production Thomas Lavergne explain how that raw footage worked its way through the edit room towards the final cut.

From a technical perspective, the first challenge was simply handling such a huge quantity of data. There was so much, Thomas explains, that it had to be transcoded to 2K for editing. "This was something we didn't have to do on Human [which Thomas worked on as post-production supervisor], which was filmed in HD," he notes.

However, as Anastasia Mikova, the film's co-director, observes, "when you work with Yann it's never just a film; it's always a project. There's the main film, which will be released in cinemas, and then there's a touring exhibition, there are documentaries we do for television specifically, things we do for the internet that go viral..." This means that any of the footage might be used in different ways, and consequently making it all manageable is not the only consideration. It also needs to remain sufficiently high quality at the same time, so that even if something should be needed for the cinema cut, the editors wouldn't need to go back to the native 4K footage. "So we chose Apple ProRes 422," Thomas reveals, "which is 10-bit and has a good size/quality ratio."

While Thomas took care of the technical aspects of post-production, Philippine's job was to watch hundreds of hours of interviews with women from all over the world and choose what material to send through to the final edit. "We get our first selection from the journalists who have done the interviews with women," she explains. "They make about an 11-hour selection [from up to 50 hours of interviews]. I have to make a second selection that Anastasia and Yann and the editor will see, because they don't have time to see the whole thing. From 11 hours, I usually cut it down to three or four hours.

"We have themes for every interview, for instance where they talk about marriage or love. My colleague Anne-Claire makes timelines where she logs each interview under those themes. Once it's ready, I watch it alphabetically. You have adolescence, adoption, then you have birth, children and so on, with about 15 minutes for each subject. I watch it all, and then I put the ones that I select in another timeline to be watched by Anastasia and Yann."

Do you own Canon kit?

Any interview footage could be selected for this timeline because all of it – no matter where in the world it was shot – was as uniform as possible, thanks to a strict protocol that all the filming crews were instructed to stick to. The production company, Hope Production, issued every crew with a comprehensive 24-page protocol document, which spelled out every camera setting required, menu by menu, and specified precisely how the interview was to be staged. A Canon EOS C300 Mark II, with a Canon EF 70-200mm f/2.8L IS II USM lens, was to be positioned 2.6 metres from the interview subject's chair; the room was to be quiet and dark, with a black backdrop, and the lighting set up exactly as specified. Strict instructions were given for the framing of the shot, with the subject's head and shoulders centred in the frame.

The cinematographers were mandated not to expose for the highlights but instead to favour the shadows even if the highlights ended up slightly over-exposed. ("Expose the highlights of white skin to 50-60% of white, depending on skin tone," the protocol document set out. "Expose dark skin to 30-50%.") The key thing was to clearly discern the facial features, reflecting the naturalistic aesthetic that Yann sought in the project.

But the protocol emphasised that the crews should not attempt to tweak exposure or contrast according to what they saw in their monitors. Instead, they had to stick to the specs and "optimise shooting for a calibration treatment, not for immediate rendering."

The protocol document issued to film teams around the world included detailed instructions about the studio setup and framing required for all of the footage.

One of the location shots, which were designed to be inserted before each interview to establish a context for the subject being interviewed.

Behind the scenes: interviewing for Woman

From the camera position to posing the tough questions, this is how the Woman team carried out their powerful interviews.

The consistency of the talking head footage gave Philippine the freedom to make her choices based purely on narrative and emotional factors – which wasn't always easy. "It's hard if you have two nice answers from the same person, saying the same thing but differently, and have to choose one. Sometimes one answer has something that the other doesn't, or vice versa. You still have to make a choice," she says. Usually it took Philippine a week to edit down each location's selection of footage, but some selections were more challenging. "Rwanda dealt with tough topics so it took me two weeks to select because I had to take breaks pretty often. It was the most [emotionally] intense selection that I've watched. But even in Rwanda, there were some funny parts about female sexuality and there's some balance between serious and light-hearted stories."

Thomas explains that they opted to shoot the widest frame available with the Canon EOS C300 Mark II, which is 4,096 x 2,160, giving an aspect ratio of 1.89. This wider frame meant that the footage had extra background compared to Ultra High-Def footage, which has an aspect ratio of 1.77. "So if we post-produce the movie in 1.77, we have the possibility to pan a bit," Thomas says, to improve the framing or just vary things a little – perhaps to linger on emotional moments – even without 'punching in' to (in effect) zoom in on the subject.

When considering the emotional impact of her role, Philippine says: "I think it would be a warning signal if I wasn't feeling anything any more. I'm glad I can feel empathy with the subjects. What's funny is sometimes I feel empathy for things that I can't relate to, like losing your child. I don't have children, but that's the one thing that makes me cry every time. There are times where I'm more detached, even if I know what I'm watching is interesting. It's like making friends. Sometimes there is chemistry between people, sometimes not."

In addition to the interviews themselves, location footage was shot in order to add some context, whether it was the interview subject's home, her place of work, or somewhere else of significance to her. Crews were instructed to shoot this outdoors in natural light if possible – ideally in the early morning or evening rather than in broad daylight. They were asked for a one-minute establishing shot, showing the subject doing something before coming to a stop and turning to face the camera.

For example, the protocol document suggested, "a woman working in the fields" might pick up some vegetables before getting up and looking at the camera. Or a dancer could execute some dance steps, then stand still and look at the camera. In the edit, a transition could then follow to the interview, which was always filmed front-on.

The crews were also asked to film some time lapse footage of the preliminary stages of the shoot – the interviewer meeting the subject, the studio being set up, people coming and going, and behind-the-scenes activity. The idea was to have this footage available to use in the edit to show the diversity of places and encounters, with everyday life going on in the background as the interview takes place.

This context and location footage was shot in widely varying lighting conditions, on a diverse range of cameras (although usually a Canon EOS C300 Mark II or EOS 5D Mark IV), sometimes even from drones. "We were filming so many different situations, we had to adjust the camera choice for each shoot session," Thomas observes, which meant for him "a post-production challenge, and not a small one!" The only common requirements were to shoot in 1.89 ratio and a minimum of 4K resolution.

Thomas explains that all of this widely disparate footage was transcoded to Apple ProRes 422 for editing, in 2,048 x 1,080 format – that is, retaining the original 1.89 ratio.

"We did a lot of colour grading tests on the native footage, but also in the 2K editing format because we may need to work directly on this for some web videos. The interviews have a black background, but most codecs can destroy the detail we needed to keep in the blacks." And again, because there were so many hours of footage, they needed codecs that would produce manageable file sizes. Fortunately, the Canon EOS C300 Mark II native video format, XF-AVC, at 410 megabits per second, "is the perfect balance between quality and size," Thomas says.

"For the edit format," he continues, "because we are editing on Avid Media Composer, it would have been natural to use its own DNxHD/HR codecs. But most of the flavours of this are 8-bit codecs (except the largest ones, but they produce files that are too big). To keep those details in the blacks, we needed to use 10-bit codecs (but not too big). Apple ProRes 422 has the ideal size/quality ratio for our needs."

On a typical shoot, the film crew might include several people – a focus puller and camera operator, say, in addition to a director of photography and the director. In the case of the interviews for Woman, in order to keep the set as intimate as possible, there was usually just a single cinematographer. With post-production so exacting, Thomas reports that there are six editing assistants in addition to him as director of post-production.

Ultimately, all the technical considerations serve the needs of the director. With all his experience of working with Yann, Thomas makes a telling observation: "Yann is above all a photographer. So the image is the way for him to express things. For the post-production team, one of our challenges is to show him the dailies as soon as possible.

"It's always good to have Yann to keep us, the post-production crew, focused beyond the merely technical aspects of an image and always to find the emotion in it."

This full-frame 30.4MP DSLR captures incredible detail, even in extreme contrast, while 4K video delivers ultra-high definition footage to the DCI standard (4096x2160). This was the B-camera on Woman, with Canon Log delivering footage as close as possible to that from Cinema EOS cameras, as well as capturing a wide dynamic range.

Lenses

A workhorse telephoto zoom lens with a durable design, a four-stop Image Stabiliser and ultra-low dispersion lens elements to ensure high contrast and natural colours. In the Woman shooting protocol document, this lens was always used with the C300 Mark II, positioned 2.6 metres from the interviewee's chair.

A professional-grade 200-400mm f/4 lens with a built-in 1.4x extender that boosts focal lengths to 280-560mm. A four-stop Image Stabiliser maximises sharpness and instinctive controls enhance handing. This lens was used by the Woman team for capturing some of the exterior contextual footage.